Process and apparatus for zinc smelting



July 16, 1940. F. e. BREYER 2,207,779

PROCESS Imp APFARATUS FOR z INc SMEL'IING I Filed May 18, 1938 3Sheets-Sheet 1 INVENTOR FRANK 6. 62571-7? BY g ATTORNEYS.

July 1 6, 1940.

F. G. BREYER PROCESS AND APPARATUS FOR ZINC SIELTIflG Filed May 18,1938.

3 Sheets-Sheet 2 INVENTOR FRANK 6.8REYEE ATTORNEYS July 16, 1940. F. G.BREYER 2,207,779

PROCESS AND XPPARATUS FOR ZINC SMELTING 7 Filed lay 18, 1958 3Sheets-Sheet 3 INVENTOR ATTORNEYS FRANK 6, 'BREYEE UNITED STATES PATENT:oFFicE PROCESS AND APPARATUS FOR ZINC SMELTmG Frank G. Breyer, Wilton,Conn.

Application May 1a, 1938, Serial No. 208,553

15 Claims. (01. 75-87) I This invention relates to the production ofingly small charges must be employed for satismetallic zinc by thesmelting of the zinc-bearing factory results. Zinc ores and reducingmateraw materials. rials supplied to the retorts must be of high' Theproduction of metallic zinc by pyrometalquality and of selected physicalcondition. There 5 lurgical processes up to a few years ago had inaremany types of zinc-bearing materials which 5 variably been accomplishedby the use of relaare not suitable. Moreover, the introduction of tivelysmall gas-tight refractory retorts or mufcharges into the many retorts,their discharge, fies which extend directly into small individual andthe drawing of liquid zinc from the small condensers. The liberation ofzinc as a vapor condensers are burdensome operations which from thesolid residues in these retorts requires require a great deal of laborin thepresence of 10 a reduction reaction at high temperature and withhigh temperatures, dust and fumes, which makes considerable absorptionof heat. The heat necworking conditions undesirable. essary to sustainthe reaction is generated by Still another disadvantageous feature ofthe the combustion of fuel, like coal, coke or gas, conventionalprocessisthat the fuel requirements outside the retorts and conductedtothe charges are very great because all of the CO generated 1 therein"through the refractory retort walls. within the retort isburned in theair and lost The condenser, luted into thefront end of the and by farthe larger portion of the heat genretortand extending out of the heatingzone erated by combustion around the retorts is wastinto cooling air, isnothing more than a tapereded. Only a relatively small portion of theheat down prolongation of the retort, or zinc liberatis conductedthrough the retort walls and into 20 ing chamber, and the zinc vaporsgenerated in the poorly heat-conducting residues for use in the retortmove directly into the condenser where reacting the charge. they arechilled and condensed to a pool of liquid These limitations of theconventional zinc zinc. A zinc furnace is a battery of theseindismelting process have long been recognized in vidual small retortsand condensers positioned the art, and various means have been triedwith 25 horizontally and enclosed in aflre brick setting the purpose ofovercoming them. Animproveand fired as a unit. ment, which involves theuse of vertical retorts Each retort and its'condenser of thisconvendeveloped by my co-workers and myself and de-; tional processconstitute essentially a single scribed in United States Letters PatentNos.

chamber or environment, and conditions in the 1,678,607, 1,680,726,1,712,132, 1,712,133, 1,811,910, 80 condenser are controlled byconditions in the 1,832,354, and 1,832,356, has served to some ex-'retort. Not only must sufficient heat to sustain tent to separate thefurnace, which eliminates the the reduction reaction be conducted intothe rezinc from the residues, from the condenser and to 'tort throughits walls, but the fumes released in permit some degree of independentcontrol of the retort must be in a condensable condition so these twostages of the process. This develop- 35 that when they reach thecondenser and are ment, however, has by-no means provided a-satischilledthe zinc content may there condense factoryzincsmeltingsystem, since thezinc releasout as a liquid pool of metal and be withdrawn ing furnacemust still produce zinc vapor in an from time to time manually,environment from which combustion gases are.

40 One of the limitations of this conventional excluded in order thatthe vapor may be con- 40 process is that combustion or firing gases mustdensed to liquid zinc when it reaches the conbe scrupulously excludedfrom the charge in a denser. This necessity still restricts the processretort, since the admission of such gases results to the use of retortsor muflles of relatively small in the formation of blue powder oruncoalesced cross section and still subjects it to limiting raw zincparticles in the condenser, instead of liquid material requirements,expensive preparation, 4,5

zinc. For example, as soon as a zinc retort cracks 'and wasteful methodsof indirect heating. and fire gases penetrate into the charge the Ifthere is any one aspect of the problem that vapors will not condense andcoalesce to liquid. may be said to be dominant when smelting zinc Inorder to avoid wasting the zinc-as oxide the by the use of equipmentcomparable in capacity charge is promptly withdrawn from the retort tothat used in lead and copper smelting, it is when this occurs. I theproblem of conducting heat into a porous .Another limitation-of theusual process is that body of charge gf any appreciable dimensions thenature of the charges supplied to the retorts without the aid of rapidlymoving fire gases, must be carefully controlled, and retorts of veryUsing the charge as an electric resistor and ll small cross sectionaccommodating corres'pond-. thereby generating heat within the chargeitself is a solution for certain types of ore, but it has not workedsatisfactorily or economically on ores of low fusion point or low zinccontent. On the other hand, if the heat could be generated by combustionof fuel in immediate and close contact with ore, the zinc could beeliminated from residues at a very rapid rate, as witness the very greattonnages of zinc eliminated from ore in a small space by the mechanicalzinc oxide process. See article by Breyer in The Mining Magazine,London, April, 1936.

Rapid elimination of the zinc by direct firing.

fuels and permits liquid metallic zinc to be re- .covered from theresulting mixture of zinc vapor,

suspended zinc compounds and combustion gases.

Another object of the invention is to provide an improved zinc smeltingprocess, and apparatus for carrying out the same, which enable thehandling of really large charges of zinc-bearing raw materials andfuels, permit the use of ores or other zinc-bearing materials of eitherlow or high grade as well as cheaper fuels, reduce the laborrequirements in zinc smelting andmaterially improve the conditions underwhich the operators of the prdcess must work.

Another object of the invention is to provide a zinc smelting processinvolving several steps which are carried out in independentlycontrolled chambers so as to avoid limitations imposed on the zincreleasing and condensing operations by known processes. 1 Another objectis to provide a process for producing both metallic zinc and zinc oxideas separate products by the fire reduction of the same charge ofzinciferous raw material.

Another object is to provide a process for smelt ing zinc from rawmaterial in which the heat ofreduction is supplied by combustion in thereleasing chamber, and which produces gaseous products having arelatively high zinc content from which metallic'zinc may be condensed.

Another object is to provide a zinc smelting process in whichzinc-bearing fumes are released from raw material in a chamber heated byinter- 1 nal combustion and the resulting fumes are subjected to rapidreduction and conditioned for effective condensation in a chambercontrolled independently of the zinc releaser.

A further object of the invention is to provide a zinc smelting. processcomprising new and improved methods and means for efficiently extractingzinc values from dilute or rich gases containvide a process which may becontrolled and adapted for changing conditions of operation and for theproduction of metallic zinc from various types of zinciferous rawmaterials.

I have found that the foregoing and other desirable features andadvantages may be accomplished by an entirely new sequence of separatelyenvironed and controlled process steps and apparatus. I have discoveredthat the introduction of a fume conditioning furnace intermediate thezinc eliminator and the condenser permits the elimination of zinc fromthe raw material, on the one hand, and the condensation of the zinc, onthe other, to be carried out independently in environments which aremaintained under individual chemical, thermal and mechanical controls,and that the resulting freedom from limitations here'- tofore imposedupon zinc smelting operations may be utilized to modify the eliminationstep or the condensation step, or both, so that metallic zinc may beproduced practicably by elimination from ore or the like in a chamberwhere combustion occurs.

. My process consists of three or more distinct stages which, thoughclosely related to each other, are susceptible of a wide degree ofvariation and. independent control. In the first stage I release zincfrom zinciferous raw material in a furnace by the action of carbonaceousreducing material, the heat of reduction being supplied by combustion inthe furnace chamber. in the furnace chamber preferably is kept in arelatively high range to influence the composition of the 'fumes'favorably and to permit large outputs of products, and the operationsincident to the elimination of the zinc preferably are con- "trolled soas to obtain relatively large concentrations of zinc in thefumes issuingfrom the fur- ,nace. The, charge is preheated to approximately thereaction temperature before introduction into the chamber. Thecombustion-supporting gas preferably is preheated, audit may be enrichedwith oxygen in order to enhance the zinc content of the fumes. In apreferred embodiment I supply a large proportion-of the heatnecessaryfor continuous reduction in the furnace by reoxidizing, orcombusting, part of the zinc vapor and carbon monoxide which havepreviously been generated from the charge. It also is advantageous whenusing certain raw materials and under certain conditions of operation toproduce both metallic zinc and zinc oxide as separate The temperatureproducts from the same charge material by treating the relatively richfumes generated during the early period of the reduction for therecovery of metallic .zinc according to my process, and thereafterburning to zinc'oxide the more dilute fumes later generated.

The fumes generated in the first stage of the process contain variableamounts of zinc vapor, carbon monoxide, carbon dioxide, nitrogen, andsuspended reoxidized zinc. The content of carbon dioxide andreoxidizedzinc depends largely upon the degree of reoxidation permittedin the furnace, and may vary from a small proportion to a verylargeproportion when reoxidation is utilized as the principal source of heatfor the reaction. These fumes, in a condition precluding satisfactorycondensation, are swept out of the furnace by pressure of the reactionproducts and are carried into a closed conditioning chamber containing agas permeable charge of very hot, active reducing material, such as lowtemperature coke, lignite char or charcoal. The reducing material hasbeen preheated, deoxidized and degasified before being contacted by thefumes from the furnace. During the flow of. fumes through this materialthe influx of appreciable quantities of air or other gases, except fromthe eliminating 75 atom-r9 3 furnace, is prevented, and heat is suppliedby means other than combustion within the chamber to sustain andcomplete the reduction of reducible constituents of the fumes in thegaseous or suspended form. The conditioning chamber provided for thispurpose is of a size, appropriate to the capacity of the connected zinceliminating furnace, which will subject the fumes passing therethroughto heating and reducing conditions for a period of time sufficient toeflect substantially complete reduction of their content of 002, H andzinc oxide. Its charge of reducing material is kept readily pervious tothe fumes so as to permit large through-puts and to avoid excessivepressure losses between the eliminating furnace and the condensers. Q

In this conditioning furnace, by the final reduction of oxidizedmaterials in theifumes with or without other special treatments, fumesfrom which liquid zinc otherwise would not be obtainable are convertedto a condensable condition. The treatment in the conditioner results inthedelivery of completely reduced, dust-free vapors to the next stage ofthe process-the condensation stage. In addition, non-uniformities in thematerials leaving the eliminating furnace can be treated variably andironed out by suitable con trol of the conditioning chamber, which maybe equipped to treat a variable supply and discharge a uniform exitproduct. In one embodiment of the process zinc waste material, such aszinc dross, zinc scrap, zinc die-castings and the like, may beredistilled by the sensible heat of the conditioned gases passing out ofthe chamber, resulting both in cooling the vapors for condensation andin enrichment of the vapor laden gases while' going to the condensingapparatus. The

gases leaving the conditioning chamber also may be subjected totreatment with sodium or other chlorides, or other surface fluxes orreducers of surface tension, in order to improve the coalescence. Instill another embodiment, traces of sulfur and other substances whichinterfere with the condensation and the quality of the metal product maybe removed by contacting the gases in the conditioning furnace withscrap iron, scrap copper or other drag-downs, corresponding toprecipitants in wet process purification process thereby eliminatingimpurities which otherwise would be condensed with or entrapped by thecondensing zinc vapors.

The condensation of fully reduced, vapor laden gases leaving theconditioning furnace may be carried out in various types of condensers.When the gases are quite low infzinc vapor two condensers in series maybe,-used to advantage-a liquid condenser and a powder condenser. In theliquid condenser, in addition to whatever cooling has occurred, e. g.,through redistillation of zinc after reduction, the vapors are contactedwith molten zinc metal to take advantage of the fl'ects of evaporation.They arethen cooled be-/ low the saturation point to collect the liquidproduct and thereafter preferably cooled rapidly in the powder condenserto deposit their residual zinc content as zinc dust, or blue powder.This powder may be returned to the upper part of the conditioningchamber to be redistilled by the sensible heat of the gases, enrichingthem to the point where a higher percentage of liquid is condensed and-alower percentage of powder. This system will ultimately come intoequilibrium and all the metal will be recovered as liquid;

When the gases in the powder condenser are quite dilute and require alarge loss of heat' through its walls, I may cool these walls by air andsubsequently use the hotair to combust fuel gases, when such are used toheat the conditioning furnace, or to blast the zinc eliminating furnace,or to preheat the solids going to either furnace.

By the use of the process described in general above I am able torelease zinc from residue by any procedure'best suited for thespecificzinc raw material. and the availability of fuels or electricpower, as a relatively concentrated fume and without regard to thecondensibility of the fumes as they leave the eliminating furnace. Thisprocess might-be said to be a fire concentration of the zinc withsubsequent reduction of the metal in gaseous suspension-in a separatefurnace. By its use all the advantages of fire concentration of zinc areto be had without the low heat economies and the collecting and hendlingand reworking costs of the ordinary process where the gases are cooleddown and the zinc and other suspended matter separated and collected,densified and reworked in another furnace as a charge for metal oroxide.

The importance of the flexibility of my new process will be readilyapparent to persons skilled. in the art. Since the elimination of thezinc from the residue may take place in directly fired furnaces theproblem of carrying heat economically into a bulk of porous ore and coalis solved. Only the final conditioning of the resulting fumes in theconditioning chamber need be accomplished by indirect or more expensiveheating methods. In this conditioning chamber heat transfer is mostly togases and solids in extremely fine suspension which, by theirvelocity,have. high transfer rates and because they are extremely finely divided,reduce easily. The process is freed from other limitations which areinherent in the usual retort practice. farge charges of zinc-bearingrawmaterials, .of almost any quality and physical condition, may betreated satisfactorily, and fuels of an inexpensive and readilyaccessible type may be used for combustion. Mechanical furnaces canbeused which will handle one hundred tons or more of zinc charge perday, the fumes from which are passed through closely controlledconditioning columns for treatment therein and thence to communicatingcondensers where they condense to liquid zinc.

Other features 'and advantages of'the invention will be made moreapparent by the ensuing detailed description of illustrative embodimentswhen considered in connection with the accompanying drawingsillustrating suitable apparatus which I have provided for practicing theinvention. In the drawings,

Figure l is a front elevation, partly in section, of a complete zincsmelting assembly, including a zinc eliminating furnace, a conditioningchamer and a condensing system together with provision for producingzinc oxide from the same charge as used in the eliminating furnace.

Figure 2 shows an assembly of another form of'apparatus which may beused instead of the Figure 4 shows another form of zinc elimi-iv natingfurnace in combination with another form 'of conditioning furnace and acondenser.

In the practice of the invention by the use of apparatus of the typesillustrated in the several 'figures of the drawings, the elimination ofzinc from residue is carried out in a furnace chamber designatedgenerally by the character A, and the furnace fumes from the zinceliminating chamber A, including zinc and zinc compounds in suspension,pass to a conditioning chamber B where reducible constituents thereofare reduced and the fumes are conditioned for condensation. From chamberB the zinc laden gases flow into condensation apparatus C where metalliczinc is recovered. Each of these stages of treatment is kept underindividual control and adapted for best performance of the whole undervarying conditions of operation, as described in greater detail below.

In the practice of the invention according to one embodiment I mayemploy a modified travelling grate furnace such as illustrated in Figurel for the elimination of zinc from the residue. The furnace is composedof suitable refractory furnace walls i0 which define chambers within thefurnace, separated by arches 29, and enclose a traveling grate uponwhich the charge of zinc-bearing raw material, reducing materials andfuel is continuously fed. The grate l2 comprises a plurality ofinterconnected sections forming a continuous conveyor, the sectionsbeing made of heat-resisting material and spaced to permit the passageof combustion-supporting gas therebetween but to prevent the sifting ofbriquetted material therethrough. This grate l2 passes over appropriatesprocket wheels l4 and I6, respectively, and beneath its upper flightair boxes i8, 20, 22 and 24 are provided which extend across the furnacestructureat appropriate intervals and serve to supply regulated streamsof combustion-supporting gas, such as air, to the under side of thegrate. The grate is arranged to pass beneath hoppers 2'6 and 28,respectively, the former for briquetted fuel and the latter forbriquettes of zinc-bearing raw material and carbonaceous reducingmaterial. Intermediate these hoppers the grate passes through a fuelignition chamber 30. Beyond hopper 28 is 'an additional combustionchamber 32, for bringing the charge to a reaction temperature, andbeyond this chamber are located larger, zinc eliminating chambers 33 and34 in which combustion and reduction of the charge take place. In thewalls of the zinc eliminating chambers, above the grate, inlets forcombustion-supporting gas are provided, for example as shown at 33a and34a, for a purpose hereinafter described.

In the operation of the furnace, as the grate moves beneath hopper 26 abed of fuel is'fed onto the grate and then carried into the fuelignition chamber 30 where it is ignited and from which combustion gasesare withdrawn through a. suitable stack 36. The bed of ignited fuel isthen carried beneath the hopper 2B for the charge materials, andbriquettes of zinc-bearing raw material, such as 'zinciferous ore, andreducing material, such as coke, are fed into the ignited bed of fuel atthis point. The layers of material are then carried into combustionchamber 32 where the entire charge is brought up to a reactiontemperature and from which gases are withdrawn through a stack 38. Asthe grate proceeds in its movement it then carries the ignitedmaterials, at a reaction temperature, into the zinc eliminating chambers33 and 34 where there occur continuous combustion, generation of heatand continuous reduction of .the zincbearing raw material withconsequent evolution of zinc-laden fumes. p In the preferred manner ofeliminating the zinc at A in Figure 1, a relatively small volume of airor other combustion-supporting gas is 5 fed upwardly into the chargethrough the grate l2, enough to keep the grate relatively cool and tomaintain active reduction in the lower portion of the charge. Theremaining oxygen necessary for combustion to keep the materials wellabove the reduction temperature is supplied by passing air, or anoxygen-enriched gas, preferably preheated as high as practicable, intothe chamer A at a point above the charge where part of the zinc vaporand carbon monoxide already generated will be reoxidized to carbondioxide and suspended particles of zinc oxide. In this manner the zinccontent of the fumes leaving the furnace may be greatly increased ascompared with a process in which the heat required for the reductionreaction is supplied substantially .entirely by burning carbon. Assumingno heat losses and all of the reaction materials preheated to reactiontemperature, the reduction would be maintained on a continuous basis,with no burning of carbon, by reoxidizing less than half of the zincvapor and carbon monoxide. In practice, when using the traveling gratetype of eliminating furnace, a part of the heat necessary to sustain thereactions is supplied by the combustion of carbon and the remainder bycombustion of zinc vapor and carbon monoxide, and fumes containing arelatively high proportion of zinc and zinc compounds arecontinuouslydischarged from sections 33 and 34' of the zinc eliminating chamber Athrough heat insulated off-takes 40 and 42. The fumes are carried by therespective off-takes into conditioning chambers B where furthertreatment takes place, as hereinafter de-' scribed, in order tocondition them for recovery of their zinc content.

tion the charge on the grate I2 is kept in chambers 33 and 34 untiltherate of reaction becomes retarded, which may occur after aboutthreefourths of the zinc content is exhausted, and it then passes intochamber 35 where it is fired by an air blast from beneath the grate. Thefumes from this chamber are then conveyed by' an ofltake 44 into aburner E for the production of zinc oxide. With this system theproportions of metallic zinc and zinc oxide produced from the charge maybe varied over a wide'range, depending upon market conditions, etc., andrequirements for both products may be supplied by the operation of thesame furnace on the same raw materials.

The fire reduction which takes place in the reduction chambers 33 and 34is capable of utilizing various types of zinc residues and fuels as theraw materials and of producing larg e' 'volwires of fumes for therecovery of metallic zinc. The temperature in these chambers is keptv ina high range to foster rapid reduction and the maintenance of pressuressufficient to drive the fumes through the other stages of the process. Asuitable balance of pressures between chambers 33 and 34 and adjacentchambers 32 and 35 can be effectedby appropriate venting of the latter.

The conditioning apparatus used in the second (ill stage of the presentprocess may be substantially the same regardless of whether azinceliminating. furnace of the type illustrated in Figures 1, 2 and 4,or of other types, is used. It preferably comprises a column ofgranulated coke or other active carbonaceous reducing material heated'to a temperature considerably above the reducing point of zinc oxide,carbon dioxide and water vapor and operated so that such compounds inthe fumes entering the column are reduced substantially entirely and theresulting gases conditioned for effective condensation of liquid zinc inthe condensation stage of the process. The carbonaceous reducing mate-.

rial is contained in a gas-tight chamber to which heat may be suppliedeither by burning fuel outside the chamberand transferring the heatthrough its walls or by making the column itself a resister in anelectric circuit and generating the required heat electrically withinthe chamber itself. Provision is made for feeding preheated anddeoxidized coke at the top of the column and for removing reducingmaterial at the bottom before its efflciency for conditioning the fumeshas been substantially impaired. The

' column itself should provide considerable space for carrying out thereduction reactions, and its heating capacity should be ample so as toensure thorough reduction of oxidized compounds in the fumes and topermit large through-puts of gases. I

The higher the temperatures maintained in the column the lower itsvolume may be per unit' gas-tight walls including an outer metallicshell 52 and an inner layer of flre brick or other refractory material54. Adjacent its top end it is formed with a restricted neck 50 which isnormally kept closed by a rotatable gate valve 58 permitting theintroduction of solid material into the chamber at will, but normallyexcluding air from the chamber. Through valve 58 the chambercommunicates with a hopper 60 for the reception of conditioningmaterialfrom a charging floor 62. The top of hopper B is usually covered by amovable gate which may be moved to an open position to permitthe'introduction ,of material into the hopper from a car 64. The lowerpart' of chamber 40 includes a restricted neck 86, also normally closedby a rotatable gate valve 68, through which material from the chambermay be discharged into a suitable receptacle on a floor 10. Since thefumes from the zinc eliminating. furnace and off-take 40 pass upwardlythrough the chamber and the conditioning material is introduced into thechamber at the top, the described arrangement provides descendingcolumns which result in eillcient utilization of the material thereinand enable easy adaptation of the rate of flow to requirements of theprocess. 7

Each conditioning chamber may include a bleeder 1| extending from thetop portion of the I chamber and controlled, for example, by a valve 1la for regulating the flow of gases therethrough, The purpose of thebleeder is to permit any oxidizing gases introduced into the top of thechamber by the charge materials to be bled off. so that passage of suchgases into the condensation apparatus with zinc laden gases may beavoided.

The heating means illustrated in Figure '1 includes an upper series ofelectrodes 12 extending into material in the chamber and a lower seriesof electrodes 14. With a column of coke in the chamber electricalcurrent may be passed through these electrodes and through the coke toraise the temperature of the material to the proper point andto maintainsuch temperatures while fumes from the releasing furnace pass throughthe chamber. Heating the column in this way permits'ready control overthe temperatures and conditionsof reaction therein. The heat required inthe column is the heat generated by reoxidation in the eliminatingfurnace plus an losses which occur after the fumes leave the eliminator.Since the materials being reduced are composed of gases and very finelydivided suspended compounds, reduction is very rapid, and heat transfer,whether from electrically heated coke or through the walls of theconditioning chamber, is efllcient. The large throughputs of materialsper unit volume of equipment and the freedom of selection of materialsin the several stages of the process render operations economical andefficient in comparison with known smelting practices.

. In addition to reducing material, such as coke, lignite, charcoal andactivated carbon, I may introduce in like manner, controlled amounts ofzinc scrap material, such as zinc dust, zincdross, zinc scrap, zincdie-castings and the like into the upper part of the conditioningchamber, 1

and redistlll the same'by means of the sensible heat of the previouslyreduced gases. I may also I introduce "drag-downs or condensationpromoters as described hereinabove. These practices accelerate thesubsequent condensation of molten zinc from the gases and at the sametime purify the scrap materials introduced into the chamber.

From the conditioning chambers 46 and 48,

whether of the type just described or of" other types to be describedbelow, completely reduced and conditioned zinc-laden gases passoutwardly through conduits 82 and 84 and thence into condensingapparatus 0, which may be of any suitable construction or, when thegases are relatively lean in zinc vapor, preferably is adapted speciallyfor efiicient recovery of metallic zinc, for example, as illustrated inFigure 2 or 4.

In the embodiment shown in Figure l, the condensing apparatus compriseschambers I6 and I8 having inside baflies which cause the gases to swirlthrough the chambers and to condense on the walls thereof and collect ina well or sump 88, whence liquid zinc may be withdrawn through a port 90adjacent a floor level 92. The chambers are cooled, for example, by fins19 or other cooling means. The residual gases from which zinc vapor hasbeen condensed are withdrawn from the condensers through stacks 94 and96 and then carried off for combustion uses or for other purposes, forexample, in the conduit 99 which also receives combustion gases fromchamber 32 of the travellinggrate furnace.

It will be noted that conduits 40 and 42 from the zinc eliminatingfurnace enter the conditioning chambers 46 and 48 at a point where theentering fumes immediately contact very hot conditioning material. Thisis important to satisfactory operation, since it prevents chilling ofthe fumes, subjects them to conditioning treatment underthe optimumcircumstances, and

avoids loss of zinc'values which otherwise might occur to anobjectionable extent upon contact-between the fumes and cooler material.

By use of the present'process, I am able to release fumes from themetalliferous charge in the zinc eliminating furnace which include whathave heretofore been considered objectionable combustion gases and tocondition these fumes before they are introduced into the condensingapparatus so that they are no longer objectionable and so that aneflicient recovery of liquid zinc is obtained. As already indicated, theprocess permits variations in the type of apparatus used in each stage.Several preferred variations are illustrated in Figures 2 to 4 of thedrawings.

Figure 2 illustrates an assembly in which a blast furnace of theslagging type is used for the elimination of zinc from zinciferous oreand in which special condensing apparatus is employed to enhance therecovery of metallic zinc from relatively lean zinc-laden fumes. Theeliminatingfurnace is designated I in Figure 2, and is constructed in awell known manner to provide a chamber A in which the reaction of acharge of fuel, ore and reducing material takes place. A

hearth I 02 is located at the bottom of the furnace chamber, and a wellI04 communicates with the hearth for the collection of lead and mattewhen rial. A header I06 for a blast of combustion- .supporting gassurrounds the furnace and is connected with a series of tuyeres I00 forthe introduction of a blast of air or other gas, preferably preheated,into the charge. Solid material forming the charge is dropped into thefurnace chamber from a bin IIO through a restricted neck I I 2,controlled by a bell valve H4. The furnace gases containing the zincleave the furnace chamber through a port H6 and a flue I I8 connectedwith a conditioning chamber I20. The chamber I20 illustrated in Figure 2is constructed like chambers 46 and 48 of Figure 1, although other typesof conditioning apparatus may be used in its place. Conditioned fumesfrom the chamber I20 leave through a flue I56 adjacent the upper end ofthe chamber. and thence pass to the condensing apparatus which isillustrated in greater detail in Figure 3. v

The condensing apparatus illustrated in Figures 2 and 3 includes aliquid condenser and a powder condenser. Chamber C is a liquid zinccondenser similar to those shown in Figure 1. Chamber D is a zinc dustor blue powder condenser with large metal surface cooling areas I50 andample baiiling I52 to settle out the last of the zinc in the reducedgases. It is providedwith conveying means, for example, a screw conveyorI54, at the bottom or hopper'portion, so that the collected powder maybe continuously or intermittently returned to the chamber .forrevolatilization by the sensible heat of the previously reduced gases.The conditioned gases-from B enter C by way of the port and flue I56.Molten metal condenses out in C anrl may be tapped off from the tap holeI 58; The partially condensed gases pass then into the blue powdercondenser D where, due to the intense cooling, the last of the zinc isdropped out. The non-condensable gases of high fuel value leave thiscondenser through a flue I60 to beused for any suitable purpose, such asin the degassing and deoxidizing. furnaces for the metalliferous chargeand the conditioning chamber coke. I may also burn it in regenerators orrecuperators to preheat the blast for the furnace A or use itconditioning for indirectly heating the conditioning chamber B insteadof the electric resistance method shown in Figure 2.

Charge materials introduced into the blast furnace I00are preheated,degasified and freed of substances which readily oxidize zinc vaporbefore introduction into the combustion chamber of the furnace. Thematerials may be prepared in this manner by the use of apparatus com-'municating with the bin IIO including a hopper,

solid materials passing through the kiln are kept in a state ofagitation, and preliminary deoxida-e tion and degasiflcation thereof arefacilitated. Burner I34 extends axially into the kiln through one of itsends so that solid materials approaching the burner are thoroughlytreated before they leave the kiln through conduit I36. Gases from thekiln pass off through a waste stack I46. Solid materials enteringconduit I36 are conveyed into bin IIO, for example, by a screw conveyorI48. By the use of apparatus of this type a suitably proportionedmixture of deoxidized, degasifled and preheated ore and carbonaceousmate-p rial maybe introduced into bin I I 0 at the desired rate, andfrom bin IIO these materials may be charged into the furnace chamberthrough restricted neck II2 simply by lowering the bell valve H4. Theconditioning material fed into chambers B may be degasified, deoxidizedand preheated and thenfed to these chambers by similar apparatus.

As fuel for burner I34, I may use powdered coal, oil or gaseous fuels,-but I, prefer to use residual gases taken off from the condensationstage of the process because of the economic advantage thus obtained. Itwill be understood that burner I34 may communicate in any suit ablemanner with a gas take-01f from a condensing apparatus, such as thetake-off I60 illustrated in Figure 3 of the drawings.

A further assembly of apparatus suitable for use in the improved processis illustrated in Figure 4. The zinc eliminating chamber A in thisfigure is the furnace of the Waelz kiln type,"in-

'cluding an elongated tube 300 that connects The kiln is usuallysupported on a preheated charge including zinciferous andcarbonaceousreducing materials and fuel into the entry end of the kiln, for example,through a delivery chute 3I4. Adjacent the lower end of the kiln theheader 304 is equipped with means 3I6 for introducingcombustion-supporting gas, preferably highly heated air, into thefurnace,

ment is provided by an indirectly fired vertical retort 200.

The waelz -type kiln is advantageous for use i in the economicalelimination of zinc from raw materials'of low grade. In operatiomaninclina tion and rate of rotation of the kiln are adopted which subjectthe charge to reaction conditions for a considerable period of time. Theconstant revolution of the kiln maintains a degree of agitation andmixing of the constituents of the charge which promotes a highelimination of their zinc content. The heat and blast require ments ofthis type of operation are relatively low because of its adaptabilityfor the reoxidation of a. large proportion of the zinc vapor and carbonmonoxide initially liberated from the charge before the gases leave thefurnace, so that the endothermic heat requirements of the reduction'reaction are substantially compensated by the exothermic reoxidation ofthe zinc and carbon monoxide. The operation of this apparatus thus.produces gases of relatively high zinc content, and the condition of thegases is such that they may be passed through a conditioning chamber Bin accordance with my-invention and there contacted with reducingmaterial while heat is supplied so as to convert them to a condensiblecondition.

The conditioning furnace illustrated in Figure 4'comprises a verticalretort 200, similar .to the conventional vertical coke retort, whichincludes one or more conditioning chambers B and is heated indirectly bythe combustion of gases. A. column 202 of coke or other reducingmaterial is maintained within chamber B, degasifled and deoxidizedreducing material being fed into the chamber through an overlying hopper204, for example as in Figure 2. A valve-controlled bleeder Il maycommunicate with the top portion conduits 2|. and H2 which supplysuitable gaseousfuel taken from a pipe 2 l4, preferably gases exitingfrom the zinc condenser system, and they also communicate with upper andlower conduits M6 and 2I8 that receive combustion-supporting gas such asair from preheating chambers 220 and 222, respectively. By this meanscornbustionmay take place alternately from the upper and lower ends ofthe flues, and the combustion gases exit through the idle chamber 220 or222 so that combustion-supporting gases later passed through the chamberbecome preheated before use. A retort of this type is described ingreater detail in United States Letters Patent No. 1,908,632.

The condensing system shown with the apparatus of Figure 4 embodiesconnected condensing chambers C and D for the condensationof liquid zincand powder, respectively. Fumes from the zinc eliminating furnace arecarried into the conditioning chamber B of the retort'through the flue320, and they pass upwardly through the column of reducing or otherconditioning material in a direction counter-current to the movement ofthe conditioning material. Heat sufiicient to sustain and complete thereactions in the chamber is supplied efllciently from the flues 208,

but without introducing oxidizing material intov the chamber or dilutingthegases flowing there- I through. The conditioned gases leave chamber Bthrough a flue 224 and .then pass into the liquid condenser 0. Here theyfirst flow through a section 230 in which the gases are cooled rapidlyto approximately their saturation temperature by intimate contact withliquid or solid zinc. The cooling at 230 may be regulated by coolingmeans 232. so that part of the zinc content of the gases is condensedand flows downwardly over bafiies or the like in contact with the risingvapors. From section 230 the gases go into a condenser 240 in which theliquid zinc is collected, and from this they pass to the powdercondenser D in which the residual zinc vapor is collectedas powder or'zinc dust. The remaining gases, containing a large proportion of carbonmonoxide, leave D through a flue 242 and may be returned to the retort200 for combustion. The blue powder collected in D is continuously orintermittently returned to the upper region of the conditioning chamberB or to the cooling section 230 of condenser C, an arrangement for thelatter including a screw conveyor 244 being illustrated in Figure ,4. Ifdesired, preheating of the air used to combust the gases in flues 208 orfor other purposes may be carried out by forcing the air through sheetmetal work surrounding the condensers C and D.

My improved process may be modified in many ways other than thosespecifically mentioned above once its freedom from limitations inherentin conventional retort smelting practice has been realized. For example,an arc furnace may be used in the first or zinc eliminating operation ofthe process with good results, particularly when non-volatile values areto be recovered from ore in addition to volatile-metals such as zinc. Agreat deal of freedom may also be used in the selection of apparatus,treatments and controls for the second or conditioning operation of theprocess and for the third operation in which the conditioned fumes areconverted to desired zinciferous products.

It will be a parent. to persons skilled in the art that my improvedprocess and apparatus are capable of practical embodiment in manydifferent forms. I therefore desire that the invention be accorded ascope suflicient to embrace equivalents, in keeping with the spirit ofthe specification and the requirements of the claims. I

, I claim:

1. In the pyrometallurgy of zinc, the process which comprises releasingzinc from a reducible zinciferous charge in a chamber and supplying heatfor the reduction by combustion of oxidizable material within thechamber, conducting the fumes including zincvapor, suspended reoxidizedsolids and combustion gases into a hot reaction zone of a separatelycontrolled and independently heated conditioning chairmen-passing thefumes in the conditioning chamber througha gas-permeable bed of hotreducing material while. supplying additional heat to reduceconstituents of the fumes without externally diluting their zinccontent, and condensing molten zinc from the conditioned gases inseparately controlled con-.

2. In the pyrometallurgy of zinc, the process which comprises releasingzinc from a reducible zinciferous charge in a chamber and supplying heatfor the reduction by combustion of oxidizable material within thechamber, conducting the fumes including zinc vapor, suspended reoxidizedsolids and combustion gases into a hot reaction zone of a separatelycontrolled conditioning chamber, contacting the fumes in theconditioning chamber with hot reducing material while supplying heat toreduce constituents thereof without externally diluting the zinccontent, contacting the reduced gases with condensation-promoting agentsin the conditioning chamber, and condensing molten .zinc from theconditioned gases in separately controlled condensing means.

3. In the pyrometallurgy of zinc, the process which comprises releasingzinc from a reducible zinciferous'charge in a chamber and supplying heatfor the reduction by combustion of oxidizable material within thechamber, conducting the fumes including zinc vapor, suspended reoxidizedsolids and combustion gases into a hot reaction zone of a separatelycontrolled conditioning chamber, contacting the fumes in theconditioning chamber with hot reducing material while supplying heat toreduce constituents thereof without externally diluting the zinccontent, contacting the reduced gases with an inorganic chloride in theconditioning chamber, and condensing molten zinc from the conditionedgases in separately controlled condensing means.

4. In the pyrometallurgy of zinc, the process which comprises releasingzinc from a reducible zinciferous charge in a chamber and supplying heatfor the reduction by combustion of oxidizable material within thechamber, conducting the fumes including zinc and zinc compounds ingaseous suspension out of the liberating chamber -and into a hotreaction zone of a separately con trolled and independently heatedconditioning chamber, passing the fumes through a porous bed of hotreducing material which moves through said'zone countercurrent to theflow of the fumes and simultaneously heating said material and fumes toreducing temperatures without supplying oxidizing substances thereto,thereafter conducting the fumes out of the conditioning chamber and intocooling and condensing means and condensing metallic zinc therefrom.

5. The process of zinc smelting which comprises reducing zinc-bearingraw material in a first chamber to produce a mixture including zincvapor, reoxidized zinc and gases capable of oxidizing zinc vapor beforecondensation thereof, flowing the mixture from the first chamber througha gas-permeable bed of hot reducing material in a second chamber'andthere heating the reducing material and mixture independently of saidfirst chamber, reducing said reoxidized zinc to zinc vapor and reducingsaid gases to non-oxidizing form without substantial external dilutionof the zinc vapor concentration of the mixture, and thereaftercondensing zinc vapor in the mixture to metallic zinc in anotherchamber.

6. The process of zinc smelting which comprises reducing zinc-bearingraw material in a first chamber to produce a mixture including zincvapor, reoxidized zinc and gases capable of oxidizing zinc vapor beforecondensation thereof,

flowing the mixture. from the first chamber through a gas permeable'bedof hot reducing material in a second chamber and there heating thereducing material and mixture independently of said first chamber,reducing said reoxidized zinc to zinc vapor and reducing said gasesitononoxidizing form without substantial external dilution of the zincvapor concentration'of the mixture, distilling zinc in the secondchamber and adding the resulting zinc vapor to the reducing mixture, andthereafter condensing zinc vapor in the mixture to metallic zinc inanother chamber.

7. The process of zinc smelting which comprises reducing zinc-bearingraw material in a first chamber to produce a mixture including zincvapor, suspended zinc compounds and gases capable of oxidizing zincvapor before condensation thereof, flowing the mixture into a secondchamber and into contact with reducing material hotter than the mixture,maintaining such contact for a period of at least several seconds andrewhich comprises releasing zinc from a reducible.

zinciferous charge in a chamber and supplying heat for the reduction bycombustion of oxidizable materialwithin the chamber, conducting thefumes including zinc vapor, suspended reoxidized solids and combustiongases into a hot reaction zone of a separately controlled conditioningchamber, passing the fumes in the conditioning chamber through agas-permeable bed of hot reducing material while supplying heatindependently of said combustion chamber to reduce constituents of thefumes without externally diluting their zinc content, thereaftercondensing molten zinc from the conditioned gases in one condenser andextracting the remaining zinc content ofthe residual gases as solidmetallic zinc in another condenser.

9. Inthe pyrometallurgy ofzinc, the process which comprises releasingzinc from a reducible zinciferous charge in a chamber and supplying heatfor the reduction by combustion of oxidizable material within thechamber, conducting the fumesincluding zinc vapor, suspended reoxidizedsolids and combustion gases into a hot reaction zone of a separatelycontrolled conditioning chamber, contacting the fumes in theconditioning chamber with hot reducing material while supplying heat toreduce constituents thereof without externally diluting the zinccontent, thereafter condensing molten zinc from the conditioned gases inone condenser, extracting the remaining zinc content of the residualgases as solid metallic zinc in another condenser, and

conveying solid metallic zinc from said other reoxidized zinc andcombustion gases into a second chamber and through a gas permeable bedof hot reducing material therein, heating said reducing material andfumes independently of said first chamber, while excluding oxidizingsubstances, and thereby reducing reducible constit uents of the fumesand conditioning the gases for condensation, and thereafter condensingmetallic zinc from the conditioned gases. I

11. The process of smelting zinc which comprises releasing zinc from azinciferous charge in a chamber by heating the charge in the presence ofreducing.material and combusting carbonaceous material, supplying mostof the heat of reduction by combustion of zinc vapor and carbon monoxidegenerated from the charge, passing the resulting fumes including zincvapor, reoxidized zinc and combustiongases into contact with hotreducing material while excluding oxidizingsubstances and therebyreducing reducible constituents thereof and conditioning the gases forcondensation, and thereafter condensing metallic zinc from theconditioned gases.

12. The process of producingmetallic zinc and zinc oxide as separateproducts from the same charge of zinciferous raw material whichcomprises releasing zinc from the charge byheating the charge in thepresence of reducing material, supplying a substantial part of the heatof reduction by combustion of zinc vapor and carbon monoxide generatedfrom the charge, passing the, resulting fumes into a separateconditioning chamber and substantially completely reducing andcondition-v ing them for condensation therein, condensing metallic zincfrom the conditioned gases, releasing additional zinc from the chargeafter the reduction reaction becomes retarded by combustion of carbon incontact therewith, and burning the resulting additional fumes to collectzinc oxide.

13. The process of smelting zinc which comprises releasing zinc from apreheated zinciferous charge in a chamber by further heating the chargein the presence of reducing material, supplying part of the heat ofreduction by combustion of carbon andthe remainder by reoxidation ofgeneration of fumes including zinc vapor and suspended reoxidedcompounds, condensing means for condensing zinc vapor to metallic zinc,separately controlled conditioning means including an enclosed bed ofreducing material intermediate the furnace and condenser for receivingsaid fumes from the furnace, conditioning the fumes for improvedcondensation of metallic zinc therefrom and passing conditioned gasesonward to the condenser, means for supplying heat to said material toconvert the fumes to reduced condition without substantial externaldilution of the zinc vapor concentration thereof, means for carryingfumes from said furnace and for introducing the same into saidconditioning means in the heated portion thereof, and means for carryingconditioned gases from said conditioning means into said condensingmeans, said condensing means including a condenser for collecting moltenzinc and another, communicating condenser for collecting zinc powder,and means for returning said powder into said conditioning means.

15. The process of zinc smelting which comprises releasing zinc from areducible zinciferous charge in a chamber and supplying heat for thereduction by combustion of oxidizable material within the chamber,conducting the fumes in--' cluding zinc and zinc compounds in gaseoussuspension out of the releasing chamber and into a hot reaction zone ofa separately controlled and independently heated conditioning chamber,deoxidizing a supply of carbonaceous reducing material for theconditioning chamber, maintaining a gas-permeable bed of the previouslydeoxidized material in said reaction zone, passing said fumes throughsaid bed and simultaneously supplying heat to said bed and fumes,without supplying oxidizing substances thereto, to reduce the zinccompounds to zinc vapor and conditioning the fumes for condensation ofmetallic zinc, thereafter conducting conditioned gases out of theconditioning chamber and into cooling and condensing means andcondensing metallic .zinc therefrom, and from time to time removingmaterial from said bed and adding fresh deoxidized material thereto sothat the material in said bed moves in a direction counter-current tothe flow of fumes therethrough.

FRANK G. BREYER.

